Abstract: A gas detector and method of operating the gas detector that includes a carbon monoxide sensor and a processor. The carbon monoxide sensor senses an environmental concentration of carbon monoxide and provides the sensed value to the processor. Upon receiving the value of the carbon monoxide level (COppm), the processor determines an alarm threshold level based upon the COppm level. Once the alarm threshold level is determined, the processor calculates the COHb percentage for the current COppm reading based upon a derived, fixed point equation. The processor activates an audible/visual indicator when the sensed COHb percentage exceeds the alarm threshold.

Abstract: An adverse condition detector that records historical data concerning the operation of the detector such that the detector can be interrogated by a technician. The microprocessor of the adverse condition detector monitors for alarm conditions and other important information related to the operation of the detector. Upon identifying an important characteristic of the detector operation, the microprocessor time stamps the information and stores the information within memory of the microprocessor. The detector includes an interface pad that is accessible from the exterior of the detector such that a technician can access the interface pad without removing the detector housing.

Abstract: An interface circuit and method for use in interconnected hazardous condition detectors is provided. This circuit and method prioritizes the various hazardous condition alarms to ensure that only the highest priority or greatest threat alarm is sounded when such a condition is detected. In this way a lower priority alarm that may be sounding will be switched to a higher priority alarm so that all interconnected detectors that have the capability will sound the higher priority alarm. This will reduce occupant confusion during a hazardous condition. The circuit and method also provides the ability to silence all interconnected detectors except for those sensing the hazardous condition to allow the occupant to locate the triggering alarm, and there for the location of the sensed hazardous condition.

Abstract: A method of testing the operational status of remotely distributed hazardous condition detectors is provided. The method utilizes the detector's self-test button to initiate a detector self-test. Once the self-test is complete, the detector's alarm is silenced and a remote self-test signal is sent to the interconnected remote hazardous condition detectors. The remote detectors, on receipt of this signal, will initiate a self-test of their own as if a user had depressed their test button. The user, with the local detector's alarm now silenced, is better able to hear the remotely interconnected detector's alarm. To verify that the remote self-test signal is received, thus verifying the operational integrity of the communications link, the remote detectors may sound an alarm pattern indicative of the receipt of the signal before initiating their self-test.

Abstract: An electronic sensing circuit for an electrochemical gas sensor cell providing high dynamic range is described. The electronic circuit utilizes an amplifier with a resistive feedback element to provide high sensitivity linear sensing of low detected gas concentrations. The electronic circuit also provides the ability to source sufficient current to prevent the electrochemical gas sensor cell from becoming biased under very high gas concentration conditions. This operation is enabled by adding a non-linear element in the feedback path of the amplifier, which non-linear element begins to conduct during the high gas concentration conditions.

Abstract: A method of testing the interconnect between remotely distributed hazardous condition detectors is provided. The method utilizes the detector's self-test button to initiate a detector self-test. Once the self-test is complete, the detector's alarm is silenced and an interconnect test signal is sent to the interconnected remote hazardous condition detectors. The transmission of this signal continues so long as the test button remains depressed. The remote detectors, on receipt of this signal, sound their alarm. The user, with the local detector's alarm now silenced, is better able to hear the remotely interconnected detector's alarm.